This invention relates to a process for the degermination of aqueous liquids to be subjected to a treatment with gas, using degerminating radiation, especially UV radiation.
Liquids, especially aqueous liquids, and in particular those from natural sources (e.g. ground water, spring water or river water) frequently contain germs, the presence or any multiplication of which is undesired for reasons of hygiene.
The required degermination can be undertaken by the addition of chemical agents, e.g. hydrazine, chlorine or chlorine dioxide. The use of such agents does not enter into consideration on health grounds in many cases, on account of their toxicity and the possible formation of chlorinated compounds.
Another method for degermination is represented by degerminating irradiation, especially with UV light. U.S. Pat. No. 5,122,496 discloses a process for catalytic removal of the nitrite and/or nitrate content in water in which this type of degermination is employed.
In this process, especially ground water, river water and spring water are to be pretreated by removal of the nitrite or nitrate which is usually contained therein. In this case, the water to be treated is initially passed, for degermination, through a container in which it is irradiated with UV light. Thereafter, it is treated with hydrogen gas and the water treated with gas is passed over a catalyst containing a metal of the platinum group; in this case, nitrite or nitrate is broken down by reaction with the hydrogen dissolved in the water, into nitrogen and water.
In spite of the degerminating treatment carried out prior to treatment with gas, an increasing contamination of the apparatuses and of the catalyst system with germs was observed.